1. Submission doc.: IEEE 802.11-15/1265r1 November 2015 Slide 1 RTS*/CTS* for UL/DL OFDMA Control Date: 2015-10-28 Authors: NameAffiliationAddressPhoneEmail Cheeha Kim POSTECH Networking & Distributed Systems Lab., Room 341, PIRL, POSTECH, Hyoja-Dong, Pohang, KOREA, 790-784 82-54-279-5655 chkim@postech.ac.kr Jiseon Leehappyjskr@postech.ac.kr Cheeha Kim, POSTECH

2. Submission doc.: IEEE 802.11-15/1265r1 November 2015 Slide 2 Abstract MU features include UL and DL OFDMA in 11ax SFD [1] To improve the channel utilization as much as possible for UL/DL in dense OBSS environment –AP functions asymmetrically AP needs to collect STA’s Tx demands to schedule UL MU STAs’ Tx efficiently This contribution proposes effective channel allocation method and efficient STA’s Tx demands report method using RTS * /CTS * (modified RTS/CTS) Cheeha Kim, POSTECH

3. Submission doc.: IEEE 802.11-15/1265r1November 2015 Cheeha Kim, POSTECHSlide 3 Backgrounds 802.11ax Spec Framework Document [1] –Multi-user (MU) features include UL and DL OFDMA –An UL MU PPDU (MU-MIMO or OFDMA) is sent as an immediate response (IFS TBD) to a Trigger frame (format TBD) sent by the AP 802.11ac standard –Mandatory support for 20 MHz, 40 MHz and 80 MHz channel widths –Optional support for 160 MHz and 80+80 MHz channel widths –RTS/CTS exchange negotiates dynamic bandwidth operation

4. Submission doc.: IEEE 802.11-15/1265r1November 2015 Cheeha Kim, POSTECHSlide 4 Backgrounds (cont’d) Bandwidth (BW) –Non-contiguous BW provides higher gain than contiguous BW [2] –Finer granularity of BW occupation (1/2, 1/4, 1/8 of 20MHz ) [3] Dense environments [4] –Configuration control by the AP can help the overall interference situation –AP could control the use of RTS/CTS for STAs associated with the AP in a way that optimizes network resources Dense OBSS environments [5] –AP and STAs might see the busy/idle state of secondary channels differently –RTS/CTS have no functionalities compensating unused secondary bands

5. Submission doc.: IEEE 802.11-15/1265r1 Motivation To utilize channels as much as possible –For DL-OFDMA Allocate all the channels if possible –For UL-OFDMA, Collect STA’s Tx demands efficiently Schedule channel allocation based on STA’s TX demands Slide 5Cheeha Kim, POSTECH November 2015

6. Submission doc.: IEEE 802.11-15/1265r1 RTS * - CTS * Configurations RTS* –AP/STA initiates transmission with RTS* Format is the same as the legacy RTS Subtype value may be defined for RTS* CTS* –CTS* is issued in response to RTS* Every STA is associated exclusively with a sub-channel (tone unit) within 20 MHz at association operation –20 MHz OFDMA building blocks can carry a mix of different tone unit sizes within each 242 tone unit boundary [1] CTS* is sent using associated sub-channel in each 20 MHz band Function of CTS* is the same as the original CTS’s plus reporting Tx demand But implemented CTS* may contain only Tx demand reports Slide 6Cheeha Kim, POSTECH November 2015

7. Submission doc.: IEEE 802.11-15/1265r1 AP-initiated Coordination DL-OFDMA in dense OBSS environment –AP sends a copy of RTS * in every 20 MHz band –Receiving STAs respond with CTS* for each accessible 20 MHz band –Based on CTS*, AP arranges DL-OFDMA channels AP is to schedule DL to meet equal data length requirement –STA’s Tx demands are reported in CTS* as well for UL-OFDMA scheduling UL-OFDMA in dense OBSS environment –Trigger* frame contains channel allocation information –Trigger* must be equal to CTS* in length Slide 7Cheeha Kim, POSTECH November 2015

8. Submission doc.: IEEE 802.11-15/1265r1 AP-initiated Coordination (cont’d) Slide 8Cheeha Kim, POSTECH November 2015 TimeDIFS Back-off 20 MHz 160 MHz CTS* 1 RTS* CTS* 1 DL DATA → STA1 DL DATA → STA3 DL DATA → STA2 CTS* 2 CTS* 3 ACK Trigger* STA1 → UL DATA STA3 → UL DATA STA2 → UL DATA ACK 160 MHz DL: To STA 1 CTS* 1 160 MHz DL data can receive & UL: To AP CTS* 3 CTS* 2 40 MHz UL: To AP CTS* 3 80 MHz UL: To AP

9. Submission doc.: IEEE 802.11-15/1265r1 STA-initiated Coordination UL-OFDMA in dense OBSS environment –Unrequested channels may be allocated based on outstanding Tx demands using trigger* along with CTS* Trigger* structure is the same as CTS* –UL STA Tx address is defined Slide 9Cheeha Kim, POSTECH November 2015 Time DIFS Back-off 20 MHz 160 MHz 40 MHz UL: To AP DATA ACK RTS* Trigger for unrequested 120 MHz UL CTS* Trigger* DATA

10. Submission doc.: IEEE 802.11-15/1265r1 Conclusion Using modified RTS/CTS coordination, efficient DL/UL-OFDMA transmission can be scheduled Slide 10Cheeha Kim, POSTECH November 2015

11. Submission doc.: IEEE 802.11-15/1265r1November 2015 Cheeha Kim, POSTECHSlide 11 References [1] 802.11-15/0132-06-00ax-spec-framework [2] 802.11-13/1058r0 Efficient wider bandwidth operation [3] 802.11-15/0354r1 Bandwidth granularity on UL-OFDMA data allocation [4] 802.11-15/0059r1 Uplink RTS/CTS Control [5] 802.11-14/1442r1 Considerations on DL OFDMA control mechanism